The present invention concerns a heat-sensitive recording material with a substrate, optionally a pigmented intermediate layer applied on the substrate, and a heat-sensitive recording layer that contains color formers and color acceptors. The present invention also concerns the use of the heat-sensitive recording material proposed here as a ticket and/or passenger ticket.
Heat-sensitive recording materials of the type described above with, for example, a sheet of paper, a sheet of synthetic paper, or a plastic film as the substrate have been well known since the early years of chemically reacting recording materials and have enjoyed steadily increasing popularity due, among other things, to the fact that their use, especially as tickets, is associated with great advantages for the issuer of the tickets. Because the color-forming components in the heat-sensitive recording process are fixed in the recording material itself, the toner-free and ink cartridge-free printers, whose operation no longer needs to be monitored by anyone, can be set up in large numbers. Accordingly, this innovative technology has been successfully implemented especially in public transportation, in buses and trains, as well as in air travel, at stadium and museum ticket counters, and in automatic parking ticket dispensers.
With the goal of improving heat-sensitive materials, especially for their use as tickets, with respect to their resistance to environmental effects, such as heat and humidity, a great many innovations have been introduced in the underlying chemistry and the manufacturing technology for producing these recording materials.
To enhance the resistance of developed thermal copies to water, aqueous alcohol solutions, and plasticizers, DE 10 2004 004 204 A1 proposes a heat-sensitive recording material whose heat-sensitive recording layer contains standard dye precursors and the combination of a phenolic color developer and a color developer based on urea-urethane.
Urea-urethane compounds are well known from EP 1 116 713 A1 and DE 692 04 777 T2 as developers, which can be used to increase the print density of developed thermal copies, including in combination with sulfonylurea, although these documents provide no indication of the outstanding effect of N-(p-toluenesulfonyl)-N′-3-(p-toluenesulfonyloxy-phenyl)urea.
The object of US 2005/0148467 A1 is a heat-sensitive recording material, which, in order to develop an irreversible print image, contains the components of at least two color forming systems, such that one of the color forming systems that is used is a chelate-type color forming system, while the other is a conventional leuco dye system. A large number of sulfonylurea compounds, including N-(p-toluenesulfonyl)-N′-3-(p-toluenesulfonyloxy-phenyl)urea, are named as a first developer, and in one embodiment, these compounds can be used in combination with urea-urethane compounds as a second developer.